1. Field of the Invention
The present invention relates to an input pen for transmitting information of designated positions as well as information of variations in writing pressure applied to a writing tip to a tablet in the field of, e.g., computer graphics.
2. Description of the Related Arts
In order to draw lines depending on the writing pressure applied to the writing tip of an input pen, in other words, to draw a thick line when a strong writing force is applied to the input pen, and a thin line when a weak writing force is applied to the input pen, pressure sensors have hitherto been arranged over the entire coordinate input area of the tablet, or alternatively a force sensor has been provided within the input pen to detect the writing pressure applied to the input pen.
However, distributing the pressure sensors over the entire coordinate input zone resulted in a complicated structure and in a difficulty in achieving exact detection of the writing pressure over the entire zone. On the contrary, disposing the pressure sensor within the input pen inevitably necessitated a cable for supplying information of writing pressure and resulted in a poor maneuverability during the input operation.
In the case of an input pen of this type, a coil for use in transmitting the information of designated positions to the tablet is composed of a wire wound directly around a magnetic core or a wire wound around a cylindrical bobbin. Inconveniently, the input pen employing such a coil often gave birth to an inadvertent contact of the wire when the coil is inserted in the bore of the pen body, and had a poor workability in inserting the coil and a possibility of breaking or severing of the wire.
The conventional input pen further involved drawbacks in that the diameter of a writing tip member and an outer barrel is enlarged and that the tip member and an inner barrel must be individually secured to the outer barrel because it is impossible to screw the inner barrel into the tip member due to intervention of the wire, thus resulting in a complicated structure as well as in complication in assembling work. Additionally, when the inner barrel is inserted into the outer barrel, the wire may possibly be damaged or even severd since the wire is forcibly clamped between a collar of the inner barrel and the bore of the outer barrel.
In the conventional input pen, a side button was fixedly mounted on the outer barrel so that a press section of the side button can be used for operating a switch on a substrate to transmit switching information to the tablet. In the case of fixedly mounting the side button on the outer barrel, however, there arose a problem of insecure switching operation due to displacement of the side button press section from its intended position confronting the switch, which is caused by a variance in relative mounting position of the outer barrel and the inner barrel.
In the conventional input pen, a base was mounted on the pen body by means of bent metal fittings disposed on the base. Thus, the mounting position of the base relative the pen body was uncertain. This resulted in an offset of the relative position between the switch disposed on the base and the side button located on the pen body, giving rise to uncertain switching operation. In addition, the bending of the metallic components was troublesome and laborious, and hence caused an increase in production costs.